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<title>WebGL - Textures - Environment Map</title>
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<body>
<div class="description">
Textured Cube using a environment emap. <br/>
</div>
<canvas id="canvas"></canvas>
</body>
<!-- vertex shader -->
<script id="vertex-shader-3d" type="x-shader/x-vertex">
attribute vec4 a_position;
attribute vec3 a_normal;

uniform mat4 u_projection;
uniform mat4 u_view;
uniform mat4 u_world;

varying vec3 v_worldPosition;
varying vec3 v_worldNormal;

void main() {
  // Multiply the position by the matrix.
  gl_Position = u_projection * u_view * u_world * a_position;

  // send the view position to the fragment shader
  v_worldPosition = (u_world * a_position).xyz;

  // orient the normals and pass to the fragment shader
  v_worldNormal = mat3(u_world) * a_normal;
}
</script>
<!-- fragment shader -->
<script id="fragment-shader-3d" type="x-shader/x-fragment">
precision highp float;

// Passed in from the vertex shader.
varying vec3 v_worldPosition;
varying vec3 v_worldNormal;

// The texture.
uniform samplerCube u_texture;

// The position of the camera
uniform vec3 u_worldCameraPosition;

void main() {
  vec3 worldNormal = normalize(v_worldNormal);
  vec3 eyeToSurfaceNormal = normalize(v_worldPosition - u_worldCameraPosition);
  vec3 direction = reflect(eyeToSurfaceNormal,worldNormal);

  gl_FragColor = textureCube(u_texture, direction);
}
</script>
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for most samples webgl-utils only provides shader compiling/linking and
canvas resizing because why clutter the examples with code that's the same in every sample.
See https://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<script src="resources/webgl-utils.js"></script>
<script src="resources/m4.js"></script>
<script>
"use strict";

function main() {
  // Get A WebGL context
  /** @type {HTMLCanvasElement} */
  var canvas = document.querySelector("#canvas");
  var gl = canvas.getContext("webgl");
  if (!gl) {
    return;
  }

  // setup GLSL program
  var program = webglUtils.createProgramFromScripts(gl, ["vertex-shader-3d", "fragment-shader-3d"]);

  // look up where the vertex data needs to go.
  var positionLocation = gl.getAttribLocation(program, "a_position");
  var normalLocation = gl.getAttribLocation(program, "a_normal");

  // lookup uniforms
  var projectionLocation = gl.getUniformLocation(program, "u_projection");
  var viewLocation = gl.getUniformLocation(program, "u_view");
  var worldLocation = gl.getUniformLocation(program, "u_world");
  var textureLocation = gl.getUniformLocation(program, "u_texture");
  var worldCameraPositionLocation = gl.getUniformLocation(program, "u_worldCameraPosition");

  // Create a buffer for positions
  var positionBuffer = gl.createBuffer();
  // Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
  gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
  // Put the positions in the buffer
  setGeometry(gl);

  // Create a buffer to put normals in
  var normalBuffer = gl.createBuffer();
  // Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = normalBuffer)
  gl.bindBuffer(gl.ARRAY_BUFFER, normalBuffer);
  // Put normals data into buffer
  setNormals(gl);

  // Create a texture.
  var texture = gl.createTexture();
  gl.bindTexture(gl.TEXTURE_CUBE_MAP, texture);

  const faceInfos = [
    {
      target: gl.TEXTURE_CUBE_MAP_POSITIVE_X,
      url: 'resources/images/computer-history-museum/pos-x.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_NEGATIVE_X,
      url: 'resources/images/computer-history-museum/neg-x.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_POSITIVE_Y,
      url: 'resources/images/computer-history-museum/pos-y.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_NEGATIVE_Y,
      url: 'resources/images/computer-history-museum/neg-y.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_POSITIVE_Z,
      url: 'resources/images/computer-history-museum/pos-z.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_NEGATIVE_Z,
      url: 'resources/images/computer-history-museum/neg-z.jpg',
    },
  ];
  faceInfos.forEach((faceInfo) => {
    const {target, url} = faceInfo;

    // Upload the canvas to the cubemap face.
    const level = 0;
    const internalFormat = gl.RGBA;
    const width = 512;
    const height = 512;
    const format = gl.RGBA;
    const type = gl.UNSIGNED_BYTE;

    // setup each face so it's immediately renderable
    gl.texImage2D(target, level, internalFormat, width, height, 0, format, type, null);

    // Asynchronously load an image
    const image = new Image();
    image.src = url;
    image.addEventListener('load', function() {
      // Now that the image has loaded make copy it to the texture.
      gl.bindTexture(gl.TEXTURE_CUBE_MAP, texture);
      gl.texImage2D(target, level, internalFormat, format, type, image);
      gl.generateMipmap(gl.TEXTURE_CUBE_MAP);
    });
  });
  gl.generateMipmap(gl.TEXTURE_CUBE_MAP);
  gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_LINEAR);

  function radToDeg(r) {
    return r * 180 / Math.PI;
  }

  function degToRad(d) {
    return d * Math.PI / 180;
  }

  var fieldOfViewRadians = degToRad(60);
  var modelXRotationRadians = degToRad(0);
  var modelYRotationRadians = degToRad(0);
  var cameraYRotationRadians = degToRad(0);

  var spinCamera = true;
  // Get the starting time.
  var then = 0;

  requestAnimationFrame(drawScene);

  // Draw the scene.
  function drawScene(time) {
    // convert to seconds
    time *= 0.001;
    // Subtract the previous time from the current time
    var deltaTime = time - then;
    // Remember the current time for the next frame.
    then = time;

    webglUtils.resizeCanvasToDisplaySize(gl.canvas);

    // Tell WebGL how to convert from clip space to pixels
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

    gl.enable(gl.CULL_FACE);
    gl.enable(gl.DEPTH_TEST);

    // Animate the rotation
    modelYRotationRadians += -0.7 * deltaTime;
    modelXRotationRadians += -0.4 * deltaTime;

    // Clear the canvas AND the depth buffer.
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    // Tell it to use our program (pair of shaders)
    gl.useProgram(program);

    // Turn on the position attribute
    gl.enableVertexAttribArray(positionLocation);

    // Bind the position buffer.
    gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);

    // Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
    var size = 3;          // 3 components per iteration
    var type = gl.FLOAT;   // the data is 32bit floats
    var normalize = false; // don't normalize the data
    var stride = 0;        // 0 = move forward size * sizeof(type) each iteration to get the next position
    var offset = 0;        // start at the beginning of the buffer
    gl.vertexAttribPointer(
        positionLocation, size, type, normalize, stride, offset);

    // Turn on the normal attribute
    gl.enableVertexAttribArray(normalLocation);

    // Bind the normal buffer.
    gl.bindBuffer(gl.ARRAY_BUFFER, normalBuffer);

    // Tell the attribute how to get data out of normalBuffer (ARRAY_BUFFER)
    var size = 3;          // 3 components per iteration
    var type = gl.FLOAT;   // the data is 32bit floating point values
    var normalize = false; // normalize the data (convert from 0-255 to 0-1)
    var stride = 0;        // 0 = move forward size * sizeof(type) each iteration to get the next position
    var offset = 0;        // start at the beginning of the buffer
    gl.vertexAttribPointer(
        normalLocation, size, type, normalize, stride, offset);

    // Compute the projection matrix
    var aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
    var projectionMatrix =
        m4.perspective(fieldOfViewRadians, aspect, 1, 2000);
    gl.uniformMatrix4fv(projectionLocation, false, projectionMatrix);

    var cameraPosition = [0, 0, 2];
    var target = [0, 0, 0];
    var up = [0, 1, 0];
    // Compute the camera's matrix using look at.
    var cameraMatrix = m4.lookAt(cameraPosition, target, up);

    // Make a view matrix from the camera matrix.
    var viewMatrix = m4.inverse(cameraMatrix);

    var worldMatrix = m4.xRotation(modelXRotationRadians);
    worldMatrix = m4.yRotate(worldMatrix, modelYRotationRadians);

    gl.uniform3fv(worldCameraPositionLocation, cameraPosition);

    // Set the matrices
    gl.uniformMatrix4fv(projectionLocation, false, projectionMatrix);
    gl.uniformMatrix4fv(viewLocation, false, viewMatrix);
    gl.uniformMatrix4fv(worldLocation, false, worldMatrix);

    // Tell the shader to use texture unit 0 for u_texture
    gl.uniform1i(textureLocation, 0);

    // Draw the geometry.
//    gl.drawArrays(gl.TRIANGLES, 0, 6 * 6);
gl.drawArrays(gl.TRIANGLES, 0, 24 * 12 * 6);

    requestAnimationFrame(drawScene);
  }
}

function generateFace(ctx, faceColor, textColor, text) {
  const {width, height} = ctx.canvas;
  ctx.fillStyle = faceColor;
  ctx.fillRect(0, 0, width, height);
  ctx.font = `${width * 0.7}px sans-serif`;
  ctx.textAlign = 'center';
  ctx.textBaseline = 'middle';
  ctx.fillStyle = textColor;
  ctx.fillText(text, width / 2, height / 2);
}

// Fill the buffer with the values that define a cube.
function setGeometry(gl) {

  var positions = [];
  var across = 24;
  var down = 12;
  for (let v = 0; v < down; ++v) {
    const v0 = (v + 0) / down * Math.PI;
    const v1 = (v + 1) / down * Math.PI;
    const s0 = Math.sin(v0);
    const s1 = Math.sin(v1);
    for (let u = 0; u < across; ++u) {
      const u0 = (u + 0) / across * Math.PI * 2;
      const u1 = (u + 1) / across * Math.PI * 2;
      positions.push(
        Math.cos(u0) * s0, Math.cos(v0), Math.sin(u0) * s0,
        Math.cos(u1) * s0, Math.cos(v0), Math.sin(u1) * s0,
        Math.cos(u0) * s1, Math.cos(v1), Math.sin(u0) * s1,
        Math.cos(u0) * s1, Math.cos(v1), Math.sin(u0) * s1,
        Math.cos(u1) * s0, Math.cos(v0), Math.sin(u1) * s0,
        Math.cos(u1) * s1, Math.cos(v1), Math.sin(u1) * s1,
      );
    }
  }
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
}

// Fill the buffer with normals for cube
function setNormals(gl) {
  var normals = [];
  var across = 24;
  var down = 12;
  for (let v = 0; v < down; ++v) {
    const v0 = (v + 0) / down * Math.PI;
    const v1 = (v + 1) / down * Math.PI;
    const s0 = Math.sin(v0);
    const s1 = Math.sin(v1);
    for (let u = 0; u < across; ++u) {
      const u0 = (u + 0) / across * Math.PI * 2;
      const u1 = (u + 1) / across * Math.PI * 2;
      normals.push(
        Math.cos(u0) * s0, Math.cos(v0), Math.sin(u0) * s0,
        Math.cos(u1) * s0, Math.cos(v0), Math.sin(u1) * s0,
        Math.cos(u0) * s1, Math.cos(v1), Math.sin(u0) * s1,
        Math.cos(u0) * s1, Math.cos(v1), Math.sin(u0) * s1,
        Math.cos(u1) * s0, Math.cos(v0), Math.sin(u1) * s0,
        Math.cos(u1) * s1, Math.cos(v1), Math.sin(u1) * s1,
      );
    }
  }
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(normals), gl.STATIC_DRAW);
}

main();
</script>
</html>



